This invention relates to marine vessels, but more specifically, to a method and/or an apparatus to improve efficiency of operation of a marine vessel by reducing skin friction drag or wetted area resistance while underway in order to provide more cost-effective marine transport services.
Fuel costs have suppressed growth of water transport services and leisure boating. In some cases marine transport services are cost prohibitive unless relegated to slower non-planing hull vessels such as pontoon boats, electric boats and the like operating on routes less than a few miles. Rising fuel cost is the primary obstacle as many vessels require several hundred to thousands of horsepower. Large commercial shipping vessels endure high costs and simply pass them on to their customers.
In the past, certain efforts to improve efficiency have been directed to reducing wetted area resistance of the ship's hull in order to lower frictional drag, horsepower requirements, and/or provide a higher hull or planing speeds. Drag due to wetted area resistance increases with velocity and the area of the wetted surface. To reduce drag, planing hull vessels reduce the area of the hull in contact with water by raising the bow. Other planing hull designs (e.g., a stepped hull configuration) provide hull ventilation to reduce the effective surface contact and wetted area resistance. Other attempts to reduce wetted area resistance include injecting air bubbles around submerged portions of the hull, providing air cushion beneath a hull (surface effect ships), and/or creating bubbles by negative pressure (venturi effect) and then routing the air bubbles to desired regions of hull. U.S. Pat. Nos. 5,534,568; 6,789,491; 7,219,614; 6,606,959; 5,452,676; 6,948,439; and patent publication nos. 2001/0022152; and 2002/0014192; exemplify such prior systems. Injecting air bubbles from the atmosphere requires substantial power, hull plumbing and orifices to route bubbles, which are subject to marine fouling. In addition, injecting air bubbles may induce unwanted cavitation in the region of the propeller. It may also be undesirable for a manufacturer to modify molds to incorporate hull plumbing. Surface effect ships have substantially flat hull bottoms thereby sacrificing smooth rides in rough seas.